Heretofore, copolymers of chlorinated polyvinyl chloride and vinyl acetate were generally produced by solution polymerization and had unsuitable properties, such as low temperature stability, for utilization in the production of magnetic tapes.
U.S. Pat. No. 2,332,974, to Lytton, et al relates to a chlorinated copolymer of vinyl chloride and vinyl acetate which is prepared via solution polymerization.
U.S. Pat. No. 2,989,415 to Horton relates to a magnetic recording media made from copolymers of butadiene and acrylonitrile.
U.S. Pat. No. 3,100,762 to Shockney relates to a specific post-halogenation of polyvinyl chloride resins or copolymers thereof wherein chloroform and ultraviolet illumination were utilized.
U.S. Pat. No. 3,627,853, to Bond, et al relates to a specific process for chlorinating suspension polymerized copolymers of vinyl chloride and vinyl acetate by adding the comonomer when at least 40 percent by weight of the vinyl chloride has been converted to polymer, the amount of the comonomer being less than the amount of the remaining unreactive vinyl chloride and subsequently polymerizing the mixture of the remaining vinyl chloride and copolymer at an elevated temperature and conducting after chlorination according to any known technique as in suspension, solution, etc., at a temperature of from about 70.degree. to about 80.degree. C.
U.S. Pat. No. 3,650,828, to Higashi, et al relates to a mixture of a high molecular weight vinyl chloride-vinyl acetate copolymer and a thermoplastic polyurethane-polyurea, hydroxyl-functional elastomer which is a reaction product of a mixture of a polyesterdiol, a hydrocarbon diol, a diphenyl sulfone diamine and an organic diisocyanate.
U.S. Pat. No. 3,681,137 to Nagazono relates to making a magnetic powder of utilizing a binder obtained from a mixture of butyl cellulose acetate resin, a urethane prepolymer, and a urethane elastomer.
U.S. Pat. No. 3,983,302 relates to a magnetic tape having a binder containing a vinyl terpolymer as made from vinyl chloride, vinyl acetate and glycol monoacrylate, and a diisocyanate.
A German article "Uber die Chlorierung von Polyvinylacetat und von Polymethacrylsauremethylester" by Von W. Hahn and F. Grafmuller date July 2, 1956, relates to chlorination of polyvinyl acetate or polymethyl methacrylate at relatively low temperatures.